Synthetic and Structural Studies of [FeFe]-Hydrogenase Models Containing a Butterfly Fe/E (E = S, Se, or Te) Cluster Core. Electrocatalytic H₂ Evolution Catalyzed by [(μ-SeCH₂)(μ-CH₂NCH₂Ph)]Fe₂(CO)₆

Abstract

As models of [FeFe]-H2 ases, 13 butterfly Fe/E (E = S, Se, or Te) complexes (1–13) have been prepared by various synthetic methods. Treatment of [(μ-SCH2)2CH2]­Fe2(CO)6 (A) and [(μ-SCH2)2CHO2CPh]­Fe2(CO)6 (B) with the in situ-generated N-heterocyclic carbenes (NHC) IMe/Mes, IVinyl/Mes, IMes, and IMe gave the corresponding carbene-substituted butterfly [2Fe2S] complexes [(μ-SCH2)2CH2]­Fe2(CO)5(IMe/Mes) (1), [(μ-SCH2)2CH2]­Fe2(CO)5(IVinyl/Mes) (2), [(μ-SCH2)2CHO2CPh]­Fe2(CO)5(IMes) (3), and [(μ-SCH2)2CHO2CPh]­Fe2(CO)4(IMe)2 (4), respectively. Although the N-p-methoxyphenyl-substituted 1,2,4-diselenazolidine C reacted with Fe3(CO)12 to give the expected butterfly [2Fe2Se] complex [(μ-SeCH2)2NC6H4OMe-p]­Fe2(CO)6 (5) and further reaction of 5 with PPh3 afforded its PPh3-substituted derivative [(μ-SeCH2)2NC6H4OMe-p]­Fe2(CO)5(PPh3) (6), the N-arylmethyl-substituted 1,2,4-diselenazolidines D–F reacted with Fe3(CO)12 to give the first butterfly [2Fe1Se1N1C] complexes [(μ-SeCH2)­(μ-CH2NR)]­Fe2(CO)6 (7, R = PhCH2; 8, R = NC5H4CH2-p; 9, R = CpFeC5H4CH2), unexpectedly. More interestingly, on the basis of synthesizing the first ODTe-bridged butterfly [2Fe2Te] complex [(μ-TeCH2)2O]­Fe2(CO)6 (10), the NHC-substituted butterfly [2Fe2Te] complexes [(μ-TeCH2)2O]­Fe2(CO)5(L) (11, L = IMe/Mes; 12, L = IMes; 13, L = IMe) were prepared by reactions of complex 10 with the corresponding NHC ligands. In addition, while all of the new complexes 1–13 were structurally characterized, complex 7 was found to be a H2-producing catalyst from benzoic acid and p-toluenesulfonic acid under cyclic voltammetry conditions.

Di-, tri- and tetraphosphine-substituted Fe/Se carbonyls: synthesis, characterization and electrochemical properties

“…Also, many studies have shown that replacing sulfur with a selenium atom in some hydrogenase models has special advantages in the hydrogen evolution reaction (HER). 38–54 Weigand and Song et al . reported that Se-containing models could increase the electron density around the iron centers and reduce the reduction potential compared to the sulfur analogues.…”

“…Also, many studies have shown that replacing sulfur with a selenium atom in some hydrogenase models has special advantages in the hydrogen evolution reaction (HER). [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] Weigand and Song et al reported that Se-containing models could increase the electron density around the iron centers and reduce the reduction potential compared to the sulfur analogues. Weigand found that the hexacarbonyl model containing the Sn atom Fe 2 [μ-(SeCH 2 ) 2 SnMe 2 ](CO) 6 can be easily protonated by HBF 4 •Et 2 O.…”